'Rin Okumura'is the 15 year-old protagonist of the story, Rin is also the son of Satan born from a human woman and is the inheritor of his father's powers. After Satan possessed & killed his guardian, Father & Exorcist, Paladin Shirou Fujimoto, Rin decides to become an Exorcist in order to take revenge upon Satan. While being immature and childish, he will put himself in great amounts of danger for the sake of helping his friends and achieving his goal. He can tap into the power he has inherited from Satan through the use of the demon-slaying blade, Kurikara. The sheath acts as a portal to Gehenna (the demon world) which when drawn returns Rin to his true demon form.

He is currently attempting to gain the title of Meister as a Knight (an exorcist who fights with a sword) so he can make one step closer to becoming a Paladin like Shiro. He is currently ranked as an Exwire. He is also noted to be good in cooking.